Which functional group is characteristic of aldehydes?

The functional group characteristic of aldehydes is the -CHO group. In this structure, the carbon atom is bonded to a hydrogen atom and double-bonded to an oxygen atom, creating a carbonyl group (C=O) at the terminal end of a carbon chain. This specific arrangement of atoms is what distinguishes aldehydes from other carbonyl-containing compounds, such as ketones which have the carbonyl group located within the carbon chain.

The presence of the -CHO functional group is essential for identifying aldehydes in molecular structures, as they exhibit unique properties and reactivity patterns due to it. For example, aldehydes are typically more reactive than ketones in nucleophilic addition reactions due to the greater steric accessibility and electron-withdrawing effects of the hydrogen atom adjacent to the carbonyl. Understanding this functional group is foundational for recognizing and categorizing aldehydes in organic chemistry.